Manufacturers of mobile electronics such as cell phones and tablet computers face many challenges in their efforts to keep their manufacturing costs low, to minimize the size of the devices compact, and to differentiate their products from those of their competitors. Among these challenges is minimizing the number of moving parts on the device. One notable effort in this regard has been the trend toward replacing physical buttons with virtual buttons through the use of touch sensors—either on the display or on some other part of the device. A common complaint about such virtual keys, however, is that it is very easy for them to be pressed accidentally, even when the user's hand is nowhere near the device. This often occurs as a result of the device bouncing around in the user's pocket or purse.